Brown spots

Hello It looks a little like splash damage from liquids getting on the leaf and then exposure to light or a chemical reaction on the leaf surface and burning it. Watch and see if it spreads any further and then evaluate. Make sure you're doing a plain ph'd water every 3rd watering to prevent toxicities. And possibly consider getting the biobizz calmag, i saw a great change in my leaf quality after starting calmag consistently. I saw the wpm in the comment, a product i know that works well always and actually is good for bugs too is called old stage green clean, if pm is a consistent struggle consider picking up a small bottle.👍 Happy growing.